The present invention concerns a method of manufacturing an optical device having an ink film by using an ink jet printing apparatus having an ink jet head. The optical device includes mainly color filters and organic electroluminescence devices.
According to the manufacturing method of the optical device of the invention, each of layers, that is, a coloration layer of a color filter, a color transformation layer of a color transformation filter, an organic light emitting layer of an organic electroluminescence device (hereinafter also referred to as an organic EL device), or charge transporting layer can be formed, as well as, a circuit pattern of a circuit substrate, a wiring pattern of a thin film transistor, a lens pattern of a micro lens, a flow channel pattern of a biochip, etc. can also be formed.
For example, as the method of manufacturing the color filter, a photolithographic method, an etching method, etc. have been known. In the manufacturing method of the color filter by the photolithographic method, a coating film of a photosensitive resin layer for each color is formed over the entire substrate and exposed patternwise, then an unnecessary portion of the coating film is removed and a remained pattern is used as each pixel. In the method, since a lot of the coating film is removed upon development, a great amount of material is wasted. Further, since exposure and development steps are conducted on every pixels, the number of step is increased. The photolithographic method has been utilized for the manufacture not only of color filters but also of various optical devices or electric devices such as organic electroluminescence devices.
However, the substrate size of the color filter has been increased year by year. For reducing the cost of the color filter, since existent pigment dispersion method, etc. of repeating photolithographic steps result in much loss, a manufacturing method of using an ink jet head has been studied in recent years.
An ink jet printing apparatus has an ink jet head in which plural nozzles are arranged and disposed. In the ink jet printing apparatus, drawing is conducted by relatively moving nozzles and a substrate bed along the surface of the substrate bed. In the ink jet printing apparatus, considering the yield along with increase in the size of the substrate, a plurality of ink jet heads are arranged and disposed and discharge pattern information is formed so as to make the amount of a discharged liquid uniform. Further, as a method of preparing optical devices having a pattern of plural colors arranged in a stripe shape by using an ink jet printing apparatus, several methods have been known. For example, it has been known a first method of arranging the longitudinal direction of a stripe pattern and the direction of an ink jet for a specified color substantially in perpendicular to each other and causing the ink jet head to conduct main scanning along the longitudinal direction of the stripe pattern (JP-A Nos. 8-292319, and 2001-228320), or a second method of arranging the longitudinal direction of a stripe pattern and the direction of an ink jet head of a specified color substantially in parallel each other and causing the ink jet head to conduct scanning in a direction substantially perpendicular to the longitudinal direction of the stripe pattern (JP-A No. 2003-127343).
In the ink jet printing apparatus, a high positional accuracy is required for nozzles during printing. Further, fineness has become higher in display apparatus in recent years and in a case of manufacturing, for example, a color filter for use in liquid display apparatus corresponding to a full-spec high definition television (1920 row×1080 column), it is necessary to provide a higher pixel density than usual in a case of manufacture by using an ink jet printing apparatus.
However, in the first method, in a case of manufacturing an optical device or the like of high pixel density, since there is a problem that color mixing occurs when the arrangement of the ink jet head displaces even slightly and the displacement can not be amended in the course of main scanning, it was not possible to manufacture an optical device of high pixel density at a good accuracy.
On the other hand, in the second method, even in a case where color mixing occurs between pixels of different colors, failure can be prevented by changing the discharge timing of nozzles belonging to the ink jet head. However, in the second method, since the longitudinal direction of the stripe pattern and the direction of the ink jet head were in parallel, it was necessary to narrow the gap between the nozzles of the ink jet head to increase the discharging density of the ink jet head. Accordingly, when the ink jet head passes the stripe pattern, it was necessary to conduct discharge while using all the nozzles belonging to the ink jet head. However, when the nozzle density of the ink jet head is increased and discharges are conducted simultaneously from all the nozzles, vibrations of the nozzles in the vicinity affect and interfere to each other and stable discharge could not be conducted by crosstalk.
In other words, as for the ink jet head, discharged ink is usually distributed to a lot of nozzles through a common liquid chamber. Therefore, when pressure is applied to a certain nozzle and a discharge operation is performed, pressure is transmitted to an ink in other nozzles near the certain nozzle. Therefore, a discharge volume from these other nozzles becomes unstable.
In addition, at one time high driving current flows when discharge from all nozzles is performed at the same time. Therefore, ink jet head has fever by Joule heat, uniformity of discharge from a nozzle is affected.
Then, in a case of preventing the crosstalk by lowering the resolution power in the discharge, a gap results in the discharged ink pattern, to cause whitening or color shading for an identical color, which also results in a problem of failure.
The invention has been achieved for solving the foregoing problems and intends to improve the discharging accuracy and the resolution power in the manufacturing method of the optical device according to the second method described above, thereby providing a method of manufacturing an optical device free of streak-like blank or unevenness.
More specifically, it intends to improve the discharging stability and the resolution power for the gap (pitch) between a specified pixel and a pixel of an identical color adjacent with the pixel described above that constitute a stripe pattern of a color filter.